Why Might Adding An Animation Controller Cause a Character to Lose Movement?

Hi all, I'm a Unity newbie, working through this awesome tutorial to build my first 2D game. The game is a side scroller, where you control a player character, using only the <-- and --> characters (left and right arrows). The character's image is built from multiple sprites (see below). When I fire up the game and press the arrow keys, the character zips to the right and the left perfectly, as it should. But then, when I add an animation, the character properly animates, but no longer moves right or left. The animation seems to be interfering with moving the character.

First, some context: I am on Unity 2022.2.10f1 on a Windows 11 machine. My version of Microsoft Visual Studio is Version 17.5.3.

Now to describe my character. (Her name is "Eater", as she's a girl who races left and right across the bottom of the screen trying to catch and eat food that is randomly dropping from the sky.) As I said, the Eater character is made up of multiple sprites. In an attempt to keep organized, I hierarchically placed those sprites in parent containers. (See "Character Heirachy" image, attached) The following code is attached to the player to cause her to move:

Code (CSharp):

1.     void Start()
2.     {
3.         rb = GetComponent<Rigidbody2D>();
4.         anim = GetComponent<Animator>();
5.     }
6.  
7.     // Update is called once per frame
8.     void Update()
9.     {
10.         if (input != 0)
11.         {
12.             // Player is moving
13.             anim.SetBool("isRunning", true);
14.         }
15.         else
16.         {
17.             anim.SetBool("isRunning", false);
18.         }
19.  
20.         if (input < 0)
21.         {
22.             // Player is moving right
23.             transform.eulerAngles = new Vector3(0, 0, 0);
24.         }
25.         else if (input > 0)
26.         {
27.             // Player is moving left
28.             transform.eulerAngles = new Vector3(0, 180, 0);
29.         }
30.     }
31.  
32.     private void FixedUpdate()
33.     {
34.         // We use FixedUpdate() (not Update()) because the Player object uses RigidBody 2D Physics
35.         input = Input.GetAxisRaw("Horizontal");
36.         // Move the player:
37.         rb.velocity = new Vector2(input * speed, rb.velocity.y);
38.     }

This all works just great. The script is attached to the "Eater Character" game object, which is the top object in the hierarchy.

But then, I created an Animation Controller with two Animations ("Idle" and "Running") and got the transitions to work just how I want them. So far, so good.

But when I attach the Animation Controller to "Eater Character" - the same object where I attached the C# script - something weird happens. Now when I play the game, the Eater character animates just fine in both her Idle and Running states. If I push the <-- or --> keys, she'll turn to face the direction that I wish to go. But she never physically moves left or right! She simply remains locked in position.

If I remove the Animation Controller, I revert back to the original behavior - the character can move just fine. Adding the Animation Controller seems to be interfering with movement.

(See image "Components" for a view of both the C# script and the Animator Controller in the Component Inspector)

I know this is prob not enough information, but does anyone see what I'm doing wrong? Thank you.